Area Forecast Discussion
Issued by NWS Medford, OR

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000 FXUS66 KMFR 050400 AFDMFR Area Forecast Discussion National Weather Service Medford OR 800 PM PST Thu Mar 4 2021 .DISCUSSION...05/00Z NAM in. 05/00Z GFS in through 78hr. Strong winds have developed across the Medford forecast area, with the strongest winds along the coast, and in the Rogue and Shasta valleys. Winds will pick up later east of the Cascades. Very little in the way of precipitation so far, at least over the land areas. A long wave upper level trough is now lined up near 130W, and the associated cold front is poised off the Pacific Northwest coast. The front has become parallel to the upper level flow, and weak short waves are moving north along the frontal boundary. This will slow the eastward progress of the front quite a bit, and it may actually retrograde a bit before it moves onshore late Friday morning. So, this will be an extended wind episode. The front will move through the Medford forecast area through the rest of the day Friday, finally clearing to the east of the area Friday night. The front will weaken as it moves through the east side, so winds will begin to weaken even before the front moves through. High Wind Warnings and Wind Advisories are in effect until late Friday morning along the coast, and until Friday evening east of the Cascades. See NPWMFR for details. As far as precipitation goes, moisture from an atmospheric river will be pulled into the area as the front moves onshore, but the duration of the event will only be around 12 to 18 hours. Usually snow levels don`t drop until the front has moved through, and by that time precipitation is diminishing. However, the models are indicating cold air wrapping around bringing snow levels down before the tail end of the front is through. This would bring low end warning snow amounts to western Siskiyou county with snow levels dropping to around 3000 feet. Confidence is not high at this time with any aspect of this event. The upper level trough will move onshore Saturday morning in a weakened state and will clear to the east of the area by Saturday afternoon. Showers will decrease Friday night through Saturday with snow levels dropping to near the valley floors west of the Cascades early Saturday morning. However, current road temperatures are in the 80s along the I-5 corridor, and any snow that falls on anything that isn`t insulated from the ground will melt very quickly. The post frontal break will be short, as the next front will move onshore Sunday. Extended Discussion from the Thursday afternoon AFD...Sunday 07 Mar through Thu 11 Mar 2021. Not much has changed in the overall scheme of things. Confidence is high a fairly active pattern will continue during the forecast period. However it may not be all that bad overall. It won`t be completely dry, but there could be larger periods of dry time. By next week, storms originating from the Gulf of Alaska will drop down into the Pacific northwest. Typically these result in cooler and unsettled weather. A cold front will weaken as it moves onshore Sunday which is being supported by operational ECMWF and GFS, thus limiting the amount of precipitation, especially inland away from the coast and coastal mountains. This is also being supported by the ensembles and individual ensemble members. Monday through Tuesday, the general consensus is for the upper low to drop in from the northwest, but remain offshore Monday night into Tuesday which should keep precipitation at a relative min during the morning, then increasing in the afternoon and early evening hours. Even then precipitation is not expected to be significant enough where it`s going to cause major issues for the higher passes. Some snow will accumulate over the higher passes, but not enough where it`s going to be a concern. While the exact timing this far out could vary over time, we are confident it will remain cool and unsettled Wednesday and Thursday. Not only the operational ECMWF and GFS show this, but so do the individual ensemble members of the ECMWF and GEFS. Precipitation amounts during this time are not expected to be significant at any one time during this period which will help to limit road snow concerns, especially during the daylight hours. Some snow will accumulate at night for the higher passes and possibly the lower passes on I-5 between Grants Pass and Canyonville. However, since its early to mid March, the longer daylight hours and higher sun angle should result in little or no road snow for the lower passes, at least during the daytime. -Petrucelli && .AVIATION...For the 05/06Z TAF Cycle...The main concern during the TAF period will be low level wind shear for the coast, including North Bend and inland westside, including Roseburg and Medford. Right now, the strong winds have surfaced at most of these airports, which is precluding the need for the wind shear. However, once the winds at the surface die off, the wind shear will likely re- establish in these locations (as well as for other west side Valley airports). Additionally, strong southeast to south winds will also impact south to north oriented valleys such as the Shasta Valley, and across the higher terrain, and some low level turbulence should be generally expected. Low level wind shear is not expected east of the Cascades due to moderate to strong winds aloft mixing down to the surface. VFR ceilings and visibilities are generally expected through the TAF period, but there`s a chance that they become MVFR as the front slowly moves ashore. So areas along the coast may see it this evening into tonight, West of the Cascades tomorrow morning and East of the Cascades Friday afternoon. Areas of terrain obscuration are expected anywhere it is raining. -Schaaf && .MARINE...Updated 800 PM PST Thursday 04 Mar 2021...Strong gales and periods of storm force winds are expected this evening into Friday morning along with very steep wind driven combined seas peaking in the 17 to 27 foot range. While storm conditions should remain beyond 10 nm from shore, storm force gusts are possible elsewhere, especially in the vicinity of headlands and capes. The highest combined sea heights are most likely to occur about 20NM west of Bandon and the lowest along and near protected portions of the coast. Wave models have returned to indicating the possibility of a west- northwest swell peaking in the 13 to 19 foot by 16 second range Sunday into Monday. Thereafter, seas are expected to fall to below 10 feet on or about Tuesday. -Schaaf && .MFR WATCHES/WARNINGS/ADVISORIES... OR...High Wind Warning until 7 PM PST Friday for ORZ030-031. Wind Advisory until 7 PM PST Friday for ORZ029>031. High Wind Warning until 10 AM PST Friday for ORZ021-022. High Surf Advisory until noon PST Friday for ORZ021-022. Wind Advisory until 1 PM PST Friday for ORZ026. CA...Wind Advisory until 7 PM PST Friday for CAZ084-085. Winter Storm Watch from Friday afternoon through late Friday night above 3000 feet in the for CAZ080. Winter Weather Advisory from 4 PM Friday to 4 AM PST Saturday above 4500 feet in the for CAZ082. High Wind Warning until 7 PM PST Friday for CAZ081. Pacific Coastal Waters...Gale Warning until 10 AM PST Friday for PZZ350-356-370-376. Hazardous Seas Warning from 10 AM to 7 PM PST Friday for PZZ350-356-370-376. Storm Warning until 10 AM PST Friday for PZZ370-376. $$ 15/15/13 is the U.S. government's official web portal to all federal, state and local government web resources and services.